The proposed study An Assessment of Liver Disease in HIV-infected and HIV/HBV co-infected Tanzanians aims to assess liver fibrosis in HIV/HBV co-infected as well as HIV and HBV mono- infected individuals in Dar es Salaam, Tanzania. Despite the high burden of HIV/HBV co- infection in sub-Saharan Africa (SSA), there has been very little study of liver disease in HIV/HBV co-infected individuals in these settings. The safety and efficacy of HBV-active therapies has also yet to be determined. Africans with HIV/HBV may be at significantly greater risk of liver disease than co-infected individuals in developed countries because they are infected with HBV much longer than HIV and are frequently exposed to other competing risks of liver injury. In this study, liver disease will be examined in HIV, HBV and HIV/HBV co-infected individuals before and after initiation of HBV-active therapies to determine the amount of liver disease at baseline and the effect of HBV-active therapies on liver disease progression. Liver disease will be assessed using two non-invasive serum markers of liver fibrosis and cirrhosis, aspartate aminotransferase (AST)-to-platelet ratio index (APRI) and Fib-4. We will compare results of individuals with HIV and HBV mono-infection to those with HIV/HBV co-infection to determine whether the risk of liver disease is higher among co-infected individuals (in whom liver disease is known to be accelerated) and whether their liver disease is less responsive to therapy. Renal toxicity of the HBV-active antiretroviral tenofovir (TDF) in HIV/HBV co-infected individuals will also be assessed. This proposal, one of the largest of its kind, is aimed to improve the current gap in understanding of liver disease in these vulnerable populations in SSA.